Communications Network for Distributed Sensing and Therapy in Biomedical Applications

ABSTRACT

An implantable medical device system is provided with multiple medical devices implanted in a patient&#39;s body and a wireless mesh communication network providing multiple communication pathways between the multiple medical devices. A communication pathway between a first and a second implanted device of the multiple medical devices can comprise one or more of the other implanted multiple medical devices.

CROSS REFERENCE TO PRIORITY APPLICATION

This application is a continuation application of U.S. application Ser.No. 11/739,388 filed Apr. 24, 2007, now allowed, which claims priorityto application Ser. No. 60/805,787, filed Jun. 26, 2006 and entitled,“Communications Network for Distributed Sensing and Therapy inBiomedical Applications”, which is incorporated by reference herein.

TECHNICAL FIELD

The invention relates generally to implantable medical device systemsand, in particular, to a communications network for use with implantablesensing and/or therapy delivery devices organized in a distributed, meshnetwork.

BACKGROUND

A wide variety of implantable medical devices (IMDs) are available formonitoring physiological conditions and/or delivering therapies. Suchdevices may includes sensors for monitoring physiological signals fordiagnostic purposes, monitoring disease progression, or controlling andoptimizing therapy delivery. Examples of implantable monitoring devicesinclude hemodynamic monitors, ECG monitors, and glucose monitors.Examples of therapy delivery devices include devices enabled to deliverelectrical stimulation pulses such as cardiac pacemakers, implantablecardioverter defibrillators, neurostimulators, and neuromuscularstimulators, and drug delivery devices, such as insulin pumps, morphinepumps, etc.

IMDs are often coupled to medical leads, extending from a housingenclosing the IMD circuitry. The leads carry sensors and/or electrodesand are used to dispose the sensors/electrodes at a targeted monitoringor therapy delivery site while providing electrical connection betweenthe sensor/electrodes and the IMD circuitry. Leadless IMDs have alsobeen described which incorporate electrodes/sensors on or in the housingof the device.

IMD function and overall patient care may be enhanced by includingsensors distributed to body locations that are remote from the IMD.However, physical connection of sensors distributed in other bodylocations to the IMD in order to enable communication of sensed signalsto be transferred to the IMD can be cumbersome, highly invasive, orsimply not feasible depending on sensor implant location. An acousticbody bus has been disclosed by Funke (U.S. Pat. No. 5,113,859) to allowwireless bidirectional communication through a patient's body. Asimplantable device technology advances, and the ability to continuouslyand remotely provide total patient management care expands, there is anapparent need for providing efficient communication between implantedmedical devices distributed through a patient's body or regions of apatient's body, as well as with devices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a wireless communication networkimplemented in an implantable medical device system.

FIG. 2 is a schematic diagram of one example of a mesh communicationnetwork including multiple implantable medical devices.

FIG. 3 is a conceptual diagram depicting the specialized roles that maybe assigned to network nodes.

FIG. 4 is a flow diagram providing an overview of the general operationof a mesh network implemented in an implantable medical device system.

FIG. 5 is a conceptual diagram of a mesh network architectureimplemented in an implantable medical device system.

FIG. 6 is a conceptual diagram of a channel plan implemented by the meshnetwork.

DETAILED DESCRIPTION

The present invention is directed to providing a communications networkimplemented in an implantable medical device system, wherein the networkis configured as a mesh network that allows data to be routed betweenimplanted and external devices as needed via continuously availableconnections established through node-to-node routes that can includemultiple node “hops.” In the following description, references are madeto illustrative embodiments for carrying out the invention. It isunderstood that other embodiments may be utilized without departing fromthe scope of the invention. For purposes of clarity, the same referencenumbers are used in the drawings to identify similar elements. As usedherein, the term “module” refers to an application specific integratedcircuit (ASIC), an electronic circuit, a processor (shared, dedicated,or group) and memory that execute one or more software or firmwareprograms, a combinational logic circuit, or other suitable componentsthat provide the described functionality. As used herein, the term“node” refers to a device included in a wireless mesh network capable ofat least transmitting data on the network and may additionally includeother functions as will be described herein. Each “node” is a “networkmember” and these terms are used interchangeably herein. A node can beeither an implanted or an external device. The wireless mesh networkgenerally includes multiple implantable devices each functioning asindividual network nodes in a mesh architecture and may include externaldevices functioning as equal network nodes as will be further describedherein. It is recognized that an overall medical device systemimplementing a mesh communication network may further includenon-networked devices (implantable or external).

FIG. 1 is a schematic diagram of a wireless communication networkimplemented in an implantable medical device system. The wirelesscommunication network is characterized by a mesh architecture thatallows multi-hop communication across network nodes. The networkincludes multiple implantable devices 12 through 26 each functioning asa node (network member).

The network may further include external devices functioning as equalnodes. Patient 10 is implanted with multiple medical devices 12 through26 each of which may include physiological sensing capabilities and/ortherapy delivery capabilities. As will be further described herein, someof the implanted devices 12 through 26 may be implemented as specialtynodes for performing specific network functions such as data processing,data storage, or communication management functions without providingany physiological sensing or therapy delivery functions.

For example, device 12 may be a therapy delivery device such as acardiac pacemaker, implantable cardioverter defibrillator, implantabledrug pump, or neurostimulator. Device 16 may also be a therapy deliverydevice serving as a two-way communication node and may further beenabled for performing specialty network management functions such asacting as a network gateway. Device 14 may be embodied as a sensingdevice for monitoring a physiological condition and also serve as atwo-way communication node. Devices 18, 22, 24, and 26 may be embodiedas sensing devices for monitoring various physiological conditions andmay be implemented as low-power devices operating primarily astransmitting devices with no or limited receiving capabilities. Device20 may be implemented as a repeater node for relieving the powerrequirement burden of sensing device 18 for transmitting data from amore remote implant location to other network nodes. The mesh network isan n-dimensional network wherein node depth may be defined spatiallywith respect to proximity to a specialized node, such as a nodeincorporating gateway, data processing or data storage capabilities.

Implantable devices that may be included as mesh network members includeany therapy delivery devices, such as those listed above, and anyphysiological sensing devices such as EGM/ECG sensors, hemodynamicmonitors, pressure sensors, blood or tissue chemistry sensors such asoxygen sensors, pH sensors, glucose sensors, potassium or otherelectrolyte sensors, or sensors for determining various protein orenzyme levels. The mesh network communication system provided by variousembodiments of the present invention is not limited to any specific typeor combination of implantable medical devices.

The mesh network communication system allows a multiplicity of devicesto be implanted in a patient as dictated by anatomical, physiologicaland clinical need, without restraints associated with leads or otherhardwire connections through the body for communicating signals and datafrom one device to another. As such, sensors and/or therapy deliverydevices may be implanted in a distributed manner throughout the bodyaccording to individual patient need for diagnostic, monitoring, anddisease management purposes. Data from the distributed system ofimplanted sensors and/or therapy delivery devices is reliably andefficiently transmitted between the implanted devices for patientmonitoring and therapy delivery functions and may be transmitted toexternal devices as well for providing patient feedback, remote patientmonitoring etc.

The implanted devices 12 through 26 may rely on various power sourcesincluding batteries, storage cells such as capacitors or rechargeablebatteries, or power harvesting devices relying for example onpiezoelectric, thermoelectric or magnetoelectric generation of power.The mesh network allows management of communication operations to beperformed in a way that minimizes the power burden on individual devices(nodes) and can eliminate functional redundancies within the overallsystem. The distributed devices can be provided having minimal powerrequirements and thus reduced overall size. Implantable devicesfunctioning as network nodes may be miniaturized devices such as smallinjectable devices, devices implanted using minimimally invasivetechniques or mini-incisions, or larger devices implanted using a moreopen approach.

The mesh network may include external devices as shown in FIG. 1 such asa home monitor 30, a handheld device 34, and external monitoring device36. Reference is made to commonly-assigned U.S. Pat. No. 6,249,703(Stanton et. al.) regarding a handheld device for use with animplantable medical device, hereby incorporated herein by reference inits entirety. The medical device system may further include externaldevices or systems in wireless or wired communication with external meshnetworked devices such as a patient information display 32 fordisplaying data retrieved from the mesh network to the patient, and aremote patient management system 40. Physiological and device-relateddata is available to any device (node) included in the mesh network, andaggregated data can be used to provide short-loop feedback to thepatient or caregiver via the home monitor 30 and patient informationdisplay 32. The home monitor 30, in this illustrative example, includesRF receiver and long range network functionality allowing data receivedfrom the implanted network nodes to be accumulated and prioritized forfurther transmission to the remote patient management system 40 and/orpatient information display 32. The patient can respond appropriately toinformation retrieved from the mesh network and displayed on patientinformation display 32 in accordance with clinician instructions. Apatient may respond, for example, by modifying physical activity,seeking medical attention, altering a drug therapy, or utilizing thehandheld device 34 to initiate implanted device functions.

Data can also be made available to clinicians, caregivers, emergencyresponders, clinical databases, etc. via external or parallelcommunication networks to enable appropriate and prompt responses to bemade to changing patient conditions or disease states. Aggregated datacan be filtered, prioritized or otherwise adjusted in accordance withpatient condition and therapy status to provide clinically meaningfuland useful information to a clinician or remote patient managementsystem in a readily-interpretable manner. The home monitor 30 mayfunction as a network administration node receiving patient anddevice-related data from the implanted nodes in a continuous, periodic,or triggered manner and managing transmissions of the aggregated data toother networks or devices. Reference is made to commonly-assigned U.S.Pat. Nos. 6,599,250 (Webb et al.), 6,442,433 (Linberg et al.) 6,622,045(Snell et al.), 6,418,346 (Nelson et al.), and 6,480,745 (Nelson et al.)for general descriptions of network communication systems for use withimplantable medical devices for remote patient monitoring and deviceprogramming, all of which are hereby incorporated herein by reference intheir entirety.

Home monitor 30 and/or a programmer may be used for communicating withone or more of implanted devices 12 through 26 using bidirectional RFtelemetry for programming and/or interrogating operations. Reference ismade to commonly-assigned U.S. Pat. No. 6,482,154 (Haubrich et al.),hereby incorporated herein by reference in its entirety, for an exampleof one appropriate long-range telemetry system for use with implantablemedical devices.

The mesh architecture allows network communication between nodes to makemultiple hops. Communication paths between nodes illustrated in FIG. 1are only examples of some of the shortest pathways existing betweenadjacent nodes. Communication paths will exist between each node andevery other node in the network. Multiple hops may be made betweennodes, in accordance with individual node roles, node power status,channel plan and routing scheme, each of which will be further describedherein.

The mesh network is a self-configuring network in which all nodes areinitially equal status, i.e. the nodes do not function in a master-slaverelationship as provided in other kinds of networking schemes. As usedherein, the terms “self-configuration” and “reconfiguration” refer tothe network's ability to automatically adjust node roles andassignments, the network channel plan, and the network routing scheme,all of which will be further described below. “Primary” node functions,as used herein, generally refers to device functions relating to patientcare such as physiological sensing or therapy delivery functions,whereas the term “network” functions refers generally to roles,assignments or tasks that the device performs as part of the meshcommunication network. Some network nodes will be enabled to performonly network functions without any primary sensing or therapy deliveryfunctions.

Initially, the network will enter a learning mode during which thenetwork members learn about all other network members. Each nodeincludes memory allocated for storing a preliminary network rule set.The rule set defines communication priorities and may provide apreliminary channel plan. During the learning mode, individual nodes areassigned tasks or network functions based on the node functionalcapacity and power capacity relative to other network members, the nodeprimary function and the preliminary network rules. Each node learns thefunctions performed by other nodes and begins to take on specialistroles as the network learns about the overall group functionality andmembership. Node roles will be described in greater detail below.

A communications routing scheme is formed based on patient status andthe power status of each node. The routing scheme prioritizes datacommunications such that data relating to clinically significant eventsor conditions is given priority over data that does not have immediateor serious impact on the patient's well-being.

New nodes may be introduced at any time with the network performing aself-configuring re-learning process to grow “organically” and therebyincorporate the new node and adjust node roles and the routing scheme asappropriate. As such, a patient may initially be implanted with nodesfunctioning as sensing devices used to monitor physiological conditionsfor diagnostic purposes. After a diagnosis is made, a treatment plan mayinvolve implanting one or more therapy delivery devices. When a newtherapy delivery device is added, the network will perform a re-learningprocess to adjust node roles and the routing scheme to maintain nodecommunication priorities and optimal communications reliability andefficiency in accordance with the governing or an adjusted network ruleset. As new nodes are added, the new nodes would seamlessly integrateinto the network. In order to do this, the network membership, theexisting network rule set and the node's primary function and powersource would be factored into a new operating rule set, new peckingorder between nodes, new node roles, new routing scheme and new channelplan.

The mesh network is a self-healing network. Nodes may drop out of thenetwork, for example, due to power loss, deactivation, or removal fromthe patient. Sensing devices implanted for diagnostic purposes may beremoved as the patient enters a treatment plan with new therapy deliverydevices being implanted. Sensing or therapy delivery devices may bereplaced by newer models or models having expanded capabilities. When anode is removed from the network, either physically or functionally, aself-healing process will reconfigure the node roles, channel plan, androuting scheme.

An initial network rule set stored in the memory of each node atinitiation of the network may be altered or reconfigured externallythrough a designated communications channel by a network administratoror authorized personnel using an external programming device. Anexternal change to the network rules will re-trigger the learningprocess such that all node roles and the routing scheme are redefinedaccording to the new rules, current patient conditions and the powerstatus of individual nodes.

FIG. 2 is a schematic diagram of one example of a mesh communicationnetwork including multiple implantable medical devices. An implantablecardiac stimulation device 60 is coupled to a patient's heart by a lead61. In addition to components such as sensing circuitry, pulse generatorcircuitry, and timing and control modules typically included in acardiac stimulation device, device 60 includes a battery as a powersource for network communications, memory for storing network rules, anda wireless transceiver for bidirectional communication on the meshnetwork. Additional network nodes include distributed sensors 64, 66 and68. Sensors 64, 66, and 68 may be physiological sensors for monitoringblood pressure, blood or tissue chemistry, blood flow, or otherbiological signals at various implant locations. Sensors 64, 66, and 68each include a power source (which may be a storage device such asrechargeable battery or capacitor, an energy harvesting device, or astand-alone battery), a physiological sensor, and a transmitter ortransceiver for communicating on the mesh network. Sensors 64, 66, and68 may be implanted at various targeted monitoring sites without thelimitations normally associated with lead-based sensors. However, it isrecognized that network node devices may include lead-based as well asleadless devices.

Device 62 is embodied as a specialized network node for performingnetwork tasks such as data processing and storage. Device 62 is providedwithout primary physiological sensing or therapy delivery capabilities.As such device 62 generally includes a power source, a processor forexecuting communication operations, a memory for storing network rulesand patient and device data, and a transceiver for communicating on themesh network. Device 62 may receive data from sensors 64, 66, 68 as wellas cardiac stimulation device 60 and perform data processing algorithms,transmit results back to the cardiac stimulation device for use intherapy control, transmit results to an external device (node), storedata for future transmission to an external device, etc. Device 62allows hardware and functional redundancies such as data processingcapabilities and storage to be removed from the networked system,thereby allowing a reduction in the size and power requirements of otherindividual nodes. As such, sensors 64, 66, and 68 may be miniaturizedand execute primary sensing functions with minimal or no data processingand storage. Sensed data is transferred to device 62 for processing,storing or transmission to other network nodes.

FIG. 3 is a conceptual diagram depicting the specialized roles that maybe assigned to network nodes. Network node 100 represents any implanteddevice included as a member of the mesh network. Node 100 is configuredto primarily perform physiological sensing and/or therapy deliveryfunctions 102. In addition to the primary sensing and/or therapydelivery functions 102, node 100 may be assigned specialized networktasks. Examples of specialized network tasks are illustrated in FIG. 3and include, but are not limited to, network police 104, gateway 106,data processing 108, repeater 110, storage 112, scheduler 114, andhousekeeper 116. In some embodiments, implanted device 100 may beimplemented solely for purposes of performing specialized networkfunctions without being configured to perform primary sensing or therapydelivery functions 102. Other specialist node roles may include an“algorithm workhorse” node for performing complex, processing powerintensive algorithms and a “local coordinator” for coordinatingcommunication operations within localized clusters or neighborhoods ofnodes.

A node assigned the role of police node 104 is provided for monitoringinappropriate behavior of any of the network members. Inappropriatebehavior includes, for example, excessive communications in terms offrequency and/or data size, erroneous data generation, or other“deviant” behaviors. The police node 104 may be configured to have theauthority to reconfigure a node which is determined to be functioninginappropriately on the network. The reconfiguration may includetemporarily or permanently disabling the node as a network member,logically isolating the data communications from the deviant node byflagging messages with a logical identifier, allowing data to be removedfrom aggregated data upstream, or reassigning the node to a low priorityin the routing scheme and channel plan. The primary, non-networkfunctions of the deviant node may remain unchanged such that any sensingor therapy delivery operations may continue according to normal deviceoperation. In some embodiments, the police node may have the authorityto also alter the primary, non-network functions, for example ifinappropriate device function is suspected, the police node may beauthorized to temporarily or permanently suspend or alter primary devicefunctions. Alternatively the police node may issue a notice of thesuspected inappropriate function which is channeled through the networkto allow patient and/or clinician notification.

An implanted node functioning as a gateway node 106 is assigned the taskof coordinating communications with another network or device outside ofthe mesh network. The gateway node 106 may schedule, select andprioritize data being transmitted to an external network or device. Thegateway node 106 may be authorized to take control over one or morechannels for external or special data transmissions and communicate toother network members that those channels are temporarily unavailable.The gateway node 106 will execute translation, security or otherprotocols required for transferring data to another network. The gatewaynode may have a larger power source, longer communication range, andconnectivity with other network technologies such as WiFi 802.11, ZigBee802.15.4, Bluetooth, CDMA, GSM, etc. If a gateway node is not present orassigned by the network membership, then individual nodes may be enabledto communicate with external networks or devices as needed. The abilityto communicate to external devices/networks may be a programmableparameter for each node, and can be adjusted dynamically as the networkchanges.

A data processor node 108 is a node configured with greater powercapacity and/or processing power than other network members. Dataprocessor node 108 may be assigned processing tasks for other networkmembers or the network as a whole to relieve the power and processingburden of other individual network members. Data processor node 108 maybe provided with the processing power to execute complex,power-intensive algorithms that are difficult to implement insmaller-sized nodes.

A repeater node 110 provides “shortcut” connectivity to remote nodes. Asdiscussed previously in conjunction with FIG. 1, a node implanted in a“deeper layer” of the mesh network may transmit data to/from higherlayers or specialized nodes via a repeater node, thereby relieving thepower burden placed on a remote node or other intervening nodes forperforming network communications.

A storage node 112 is a node configured with greater memory capacitythan other network members and is assigned the task for storing datareceived from network members. Such data may be transmitted from storagenode 112 to other network members as appropriate. For example dataprocessor node 108, gateway node 106, or a therapy delivery node 102 maysend data requests to storage node 112.

A scheduler node 114 may perform network scheduling tasks such asscheduling data transmissions between implanted and external nodes andscheduling network “meetings.” Network “meetings” may be scheduled whenreconfiguration of the node assignments and roles is needed in responseto a change in patient condition, a change in power status of one ormore individual nodes, a change in network membership (a new nodeintroduced or an existing node removed from the network), or when newnetwork rules are programmed from an external source. In general,scheduler node 114 is assigned the task of coordinating networkactivities that involve all or any subset of network members. This taskof coordinating network activities generally includes “waking up,” orscheduling a “waking up”, of all or any subset of network members forperforming a specified activity. Network nodes are generally in alow-power “alert” state that allows them to be “woken up” by anothernetwork node. Upon receiving a “wake-up” signal, the node converts to ahigh power “awake” state ready to receive data transmissions orcommands.

A housekeeper node 116 is assigned the task of monitoring the channelplan to ensure that the plan is efficient and well-organized in terms ofthe number of nodes and communication workload assigned to each channel.The housekeeper node 116 ensures that all members have an up-to-datechannel plan and may alter the plan in response to changes incommunication priorities, patient condition and the power status ofindividual nodes.

The network roles illustrated in FIG. 3 are examples of the types ofroles that individual nodes may be assigned and though these roles havebeen described in the context of a node embodied as an implantabledevice, external devices may also be assigned specialist node roles. Anyone node may include one or more of the roles depicted and described.The roles included in a mesh communication network implemented in animplantable medical device system will vary depending on the particularapplication. The assignments of those roles can vary over the operatinglife of the medical device system as the network performsself-configuring and self-healing processes in response to changes innetwork membership, changes in network rules, changes in patient status,and changes in power status of individual nodes.

FIG. 4 is a flow diagram providing an overview of the general operationof a mesh network implemented in an implantable medical device system.At block 200, a network rule set is provided and stored in the memory ofeach system device to be included in the mesh network. The rule setdefines an initial channel plan shared by all network members andpriority communication rules. The rule set may be implemented in alook-up table and can be altered, adjusted or replaced at any time by anetwork administrator.

The rule set may include constant rules and variable rules. The variablerules are derived during self-configuring processes and are dynamicallyupdated in response to changing node membership, changes in nodeoperating and power status, and changes in patient status or asotherwise programmed by a user. The constant rules establish generallyunalterable operating network conditions.

The constant rules may apply to the channel plan (e.g., certain channelsmay be emergency-use only or reserved for external communication);message length (to set baseline for message coexistence andcommunication success); maximum message redundancy; maximum/minimumupdate rate; maximum message repeat level; controls on maximum meshdepth thereby limiting power usage due to node hopping; pre-definedpecking order for device/sensor communication; and pre-defined peckingorder for device/sensor power based attributes (e.g., a therapy deliverydevice having a primary battery may be assigned a power rating of 10,whereas a simple infrequent sensor may have a power rating in the 1-3range in accordance with the power supply for the given node or device).On infrequent occasions, constant rules included in a rule set may bealtered, for example in order to accommodate next generation nodesimplementing a new operation system or operating system updates.

At block 205, selected devices are implanted in a patient in adistributed manner, including sensing devices and/or therapy deliverydevices and optionally including specialist node devices (repeaters,data storage, data processors, etc.). When the devices are positionedwithin communication proximity to each other, and any external devicesthat are enabled to communicate on the mesh network, the mesh networkwill initiate a self-configuring process at block 210. All nodes areinitially equal entering the learning process 210. During this process210, the network “learns” the identities and capabilities (input block215) of all of its members. Individual node roles 225, a routing scheme220, and a channel plan 230 will be developed and established within theoperational constraints and communication priorities provided by thenetwork rule set and based on the functionality and power status of eachnode.

The system operates normally at block 235 carrying on sensing and/ortherapy delivery functions according to programmed operating modes. Datacommunications on the mesh network will occur during normal systemoperation 235 in response to previously scheduled, triggered, orrequested data transmissions in accordance with the established nodeassignments, routing scheme and channel plan.

Throughout normal system operation, any change in the network operatingconditions or environment, such changes in individual node status (block240), network rule set (block 245), node membership (block 250), orpatient status (block 255), can cause a reconfiguration to occur. Otherconditions that may cause the network to reconfigure may include aclinician- or other user-programmed change to the operating mode oroperating parameters of individual nodes or implementation of a nextgeneration operating system or software updates applied to the existingnodes. Automatic reconfiguration occurs by returning to learning processblock 210 wherein the current routing scheme 220, node roles 225 andchannel plan 230, variable rules included in the network rule set 200,and in some cases constant rules included in the network rule set 200,are adjusted “on-the-fly” to meet current power source capacities,communication priorities, therapy readiness needs, sensing demand, anddata throughput requirements. Although learning process block 210 andnormal operations block 235 are illustrated as two distinct blocks inFIG. 4, the learning process/reconfiguration operations of the networkare operating in a continuous dynamic manner in response to changes inthe network operating conditions or environment.

A change in the status of individual nodes (block 240) can cause dynamicadjustment of the behavior of each node. Individual node statusconsiders both power status and operational workload for any primaryfunctions related to sensing and/or therapy delivery. A change in powerstatus or device workload can result in adjustments to node roles andassignments as well as altering network communication behavior. A nodecan rescind a specialist role as a function of its power status or anincrease in its sensing or therapy workload. Network communicationbehavior of a node may be altered in response to a change in node statusby reducing communication frequency and/or reducing message length andcontent. A node entering a low-power status or reaching end-of-life maygenerate messages in a “last gasp” format. Abbreviated messages andmessage formatting allows power status and impending node death to becommunicated through the network. Predictive and preemptivereconfigurations of node assignments, channel plan, and routing schemefor the surviving network membership may be made in response to suchmessages.

During normal operation 235, nodes will each maintain routing qualityinformation summarizing communications success metrics. This routingquality information will be distributed throughout the network or withspecialist nodes on a periodic basis such that a network reconfigurationmay occur if routing quality diminishes. Dynamic optimization andadaptation algorithms will drive network changes to optimize operationalefficiency and reliability of both local and global mesh networkperformance.

An external change to the network rule set (block 245) will trigger areconfiguration process such that the node roles 225, routing scheme220, and channel plan 230 can be redefined in accordance with the newrules.

The network membership (block 250) may change as new devices areintroduced or removed. New devices may be implanted or positionedexternally to the patient within communication proximity (which may beon a “coming and going” basis as the patient moves about). Existingdevices may be removed from the network due to power loss, deactivation,or physical removal. An existing network may come into contact with asecond mesh network, for example networked external monitoring devicesin a hospital setting, and the networks may merge. As such, a membershipchange triggers a reconfiguration process in which the node roles 225,routing scheme 220 and channel plan 230 are adjusted. In some cases,communication with an adjacent network may cause self-isolation of themesh network for patient safety and security using, for example,frequency or time multiplexing or a logical group identification code.

The network may also respond to a change in patient status (block 255).Communication priorities, power allocations, and device operating statusmay all change in response to a change in patient status, which may bean adverse physiological event or a worsening, improving or changingphysiological condition.

Changes in node status, rule set, network membership, and patient statusmay occur in unpredictable and frequent manner. The network responds tothese changes by dynamically reconfiguring itself to operate inaccordance with the present conditions, even when these conditions maybe rapidly changing.

FIG. 4, as well as other diagrams and drawings presented herein areintended to illustrate the functional operation of the mesh network, andshould not be construed as reflective of a specific form of software orhardware necessary to practice the invention. It is believed that theparticular form of software will be determined primarily by theparticular devices employed in the system. Providing software toaccomplish the present invention in the context of any modernimplantable medical device system, given the disclosure herein, iswithin the abilities of one of skill in the art.

FIG. 5 is a conceptual diagram of a mesh network architectureimplemented in an implantable medical device system. The network 300 isan n-dimensional network including nodes 301 through 318 embodied asimplantable devices arranged within the three-dimensional space of thepatient's body and may include external devices. Fourth and higher orderdimensions are represented by specialized dimensional portal nodes 316and 318 which function as repeater nodes.

Interior nodes can be considered surface nodes because of theirproximity to a specialist node (gateway, data processor, data storage,etc.). Specialist nodes 301, 302 and 304 having greater power capacityand processing power can be interspersed through the mesh to providelocal “neighborhoods” or clusters of nodes, particularly more remoteclusters of nodes, with local data processing or other services. Forexample, specialist node 302 may provide data processing services foradjacent sensor nodes 310, 312, 314 and 320. Specialist node 302 maytransmit processing results back to sensor nodes 310, 312, 314 and 320as needed thereby providing a short feedback loop. Local specialistnodes can also reduce redundant device functions and potentially reduceparametric data collection for neighboring nodes. Interspersedspecialist nodes 301, 302, and 304 may also be assigned the role of“local coordinator” to control communications from remote“neighborhoods” or clusters of nodes to surface or other specializednodes. Repeater nodes 316 and 318 provide shorter pathways from suchremote nodes to interior nodes.

Communication pathways exist between all of nodes 301 through 318 withlonger pathways not shown in FIG. 5 for the sake of clarity. Some nodesmay be implemented as transmit-only nodes. Transmit-only operation canbe supervised by Aloha or other protocols for minimizing collisions oftransmitted data packets. Nodes may be enabled to alternate betweentransmit and transceiver modes of operation dynamically as a function ofnetwork operating needs, power status, and patient status.

Node hops or routes used to channel data through the mesh network 300 toa specialist node, e.g., nodes 301, 302 and 304, are dynamicallyadjusted in response to the mesh depth of a transmitting node, datathroughput, and operational overhead. Communication scheduling throughlong and tortuous routes can be used for low priority communications orinfrequent tasks, reserving shorter more efficient routes for higherpriority communications. Generally higher priority communications willrelate to patient or device-related events or conditions that can impactpatient health and safety or otherwise have an adverse affect on diseasestate or symptoms.

Communication between nodes can be synchronous or asynchronous andsecurity measures such as encryption and data splicing can be used toensure patient privacy and safety. Nodes can be addressed as an entiregroup, subset, or individuals. Node groups or individuals can bereconfigured for network functionality or reprogrammed for adjustingprimary functionality (reprogramming sensing/therapy delivery operatingmode or operating control parameters) from peripheral external nodes bya network administrator. Network configuration and/or programming dataare routed through the mesh to the appropriate nodes being addressed.The freshness, redundancy, and frequency of data collection or otherdata collection and communication operations for network nodes can bealtered or adjusted by addressing reconfiguration/programming commandsto node groups or individuals. Nodes may be reprogrammed to alterprimary sensing/therapy delivery functions in response to changes inpatient condition. Nodes may be reconfigured for network operations toreduce power consumption, e.g. while a patient is hospitalized andcoupled to external monitoring equipment, to limit mesh depth and forceshorter communication pathways or for performing other networkoptimization operations.

FIG. 6 is a conceptual diagram of a channel plan implemented by the meshnetwork. The channel plan will include multiple communication channels1-N which can be divided according to a frequency, time, or codemultiplexing. Operating frequency options include MICS, MEDS and ISMbands. Multiple nodes may be assigned to each channel and each node maybe assigned to one or more channels. For example, in the fictionalexample given, nodes 1, 2 and 3 are assigned to channels 1 and 3; nodes4 and 5 are assigned to channels 2 and 5, and channel 4 is reserved fornode 6. Channel assignments will be based on prioritization ofcommunications, frequency and size of communications, and otherapplication specific considerations. Nodes can communicate concurrentlyon adjacent or distant channels. Access to a channel will be based onmessage priority and patient condition. A node may alternate betweenopen, restricted, or highly-controlled channels based on messagepriority and patient status. As described previously, the channel plancan change dynamically based on network membership, individual nodepower status, patient status, or an external adjustment to the networkrule set.

Thus, a mesh network communication system for use with an implantablemedical device system has been presented in the foregoing descriptionwith reference to specific embodiments. It is appreciated that variousmodifications to the referenced embodiments may be made withoutdeparting from the scope of the invention as set forth in the followingclaims.

1. A computer readable medium for storing a set of instructions whichwhen implemented in an implantable medical device mesh communicationnetwork system cause the system to: perform a learning process forgathering information regarding a plurality of network memberscorresponding to the power capacity and functionality of each of theplurality of network members; assign roles to individual network membersfor performing network tasks in response to the learning process; definea channel plan in response to the learning process; and define a networkcommunications routing scheme in response to the learning process. 2.The computer readable medium of claim 1 further comprising adjusting anetwork rule set in response to the learning process.
 3. The computerreadable medium of claim 1 wherein the network rule set comprises one ormore constant rules and one or more variable rules.
 4. The computerreadable medium of claim 1 further comprising repeating the learningprocess in response to one of a change in a network rule set,introduction of a new device in the network, removal of an existingdevice from the network, a change in the primary operating status of anetwork member, a change in the power status of a network member, and achange in a patient status.
 5. An implantable medical device system,comprising: multiple implantable medical devices; means for providingwireless communication between the multiple medical devices via multiplecommunication pathways; means for monitoring a power status of each ofthe implantable medical devices; means for monitoring the functionalstatus of each of the implantable medical devices; means for monitoringa patient condition; means for receiving an adjusted rule set; and meansfor automatically configuring the network wherein the configuring meanscomprises means for defining a channel plan, assigning network tasks tothe multiple medical devices, and defining a routing scheme, and whereinthe configuring means configures the network in response to the powerstatus monitoring mean, the functional status monitoring means, thepatient condition monitoring means; and the means for receiving theadjusted rule set.
 6. The system of claim 5 further including anexternal device in communication with the multiple implanted medicaldevices via the means for providing wireless communication between themultiple medical devices via multiple communication pathways.
 7. Thesystem of claim 5 wherein a communication pathway selected between afirst implanted device and a second implanted device of the multiplemedical devices comprises at least one of the other of the implantedmedical devices.
 8. The system of claim 5 wherein at least one of themultiple medical devices is a specialist node assigned to perform anetwork communication task.
 9. The system of claim 8 wherein thespecialist node is one of: a gateway node, a data processor node, a datastorage node, a police node, a housekeeper node, a algorithm workhorsenode, a network administrator node, a scheduler node, a localcoordinator node, and a repeater node.
 10. The system of claim 5 whereinat least one of the multiple medical devices further comprises a therapydelivery module.
 11. The system of claim 5 wherein at least one of themultiple medical devices further comprises a physiological sensor.